realtime plotting pandas dataframe

animation, matplotlib, pandas, python, real-time-updates

Solution

I think the issue with your code is that you invoke `fig, ax = plt.subplots()` each time you refresh your data. This creates a new `Figure` each time, and thus you see new frames pop up.

Instead, you want to create the `Figure` outside of your `while` loop, and only refresh the `Axes` once you loaded new data.

I've used the basic example you've provided to create a self-updating `Figure`.

import pandas as pd
import matplotlib.pyplot as plt 
import datetime as dt

data = [ 
    {'timestamp': '2017-05-11 16:21:55', 'A': 0.724931, 'B': 0.361333, 'C': 0.517720},
    {'timestamp': '2017-05-11 16:22:25', 'A': 0.725386, 'B': 0.360833, 'C': 0.518632},
    {'timestamp': '2017-05-11 16:22:55', 'A': 0.725057, 'B': 0.361333, 'C': 0.521157},
    {'timestamp': '2017-05-11 16:23:25', 'A': 0.724402, 'B': 0.362133, 'C': 0.520002},
]
df = pd.DataFrame(data) 
df.set_index("timestamp")

plt.ion()
fig, ax = plt.subplots()
while True:
    dframe = df.copy()
    dframe['timestamp'] = pd.to_datetime(dframe['timestamp']) + pd.DateOffset(hours=2)
    dframe = dframe.set_index('timestamp')
    end = dframe.index.max()
    start= end.to_datetime() - dt.timedelta(hours=1)
    dframe = dframe.loc[start:end]
    plt.pause(0.0001)
    ax.plot_date(dframe.index.to_pydatetime(), dframe, marker='', linestyle='solid')

Edit 1

I cannot reproduce the raised `Warning`, but my guess would be that it's related to the `pause` call. Maybe try swapping the following and editing the pause time.

   ax.plot_date(dframe.index.to_pydatetime(), dframe, marker='', linestyle='solid')
   plt.pause(0.01)

Edit 2

Fixing the colours is quite simple. Define your colour palette and then pick from it.

colors = ['r', 'g', 'b']

plt.ion()
fig, ax = plt.subplots()
while True:
    dframe = df.copy()
    # Your data manipulation
    # ...
    dframe = dframe.loc[start:end]
    for i, column in enumerate(dframe.columns):
        ax.plot(dframe.index.to_pydatetime(), dframe[column], color=colors[i], marker=None, linestyle='solid')   
    plt.pause(0.1)

If you have more columns, add more colours to the `colors` array. Alternatively, generate it on-the-fly depending on the number of columns in `dframe`.

Problem

Original source